Oct. 11, 2004 -- Having brothers and sisters can lower a child's asthma risk, according to a new Canadian study.
The finding comes from researchers including Nicholas Anthonisen, MD, of the University of Manitoba, Canada.
Anthonisen and colleagues studied more than 170,000 children born in Manitoba between 1980 and 1990.
Nearly 14% of the children were diagnosed with asthma by age 6, with most cases diagnosed in the first two years of life.
Sibling Power and Asthma Risk
Kids with brothers and sisters had an advantage.
"Having a sibling was protective," say the researchers in the October issue of the journal CHEST. Unless the sibling had a history of allergic conditions -- such as hay fever, asthma, or eczema -- in that case asthma risk was increased.
Being born at the right time of year also helped. Children born between January and March fared best, while asthma risk was significantly higher for kids born between July and December.
Several asthma risk factors stood out, including:
- Gender. Boys were more likely to get asthma than girls.
- Location. Children in urban areas had a higher asthma risk than those in rural settings.
- Birth weight. Asthma risk was higher in kids born with low birth weight.
- Premature birth. Babies born prematurely were at higher risk for developing asthma.
- Mother's age. "The risk of asthma increased with maternal age," say the researchers.
Kids also had a higher asthma risk if they had had upper or lower respiratory tract infections during the first few years of life, and if their families had a history of allergies.
In addition, those born with certain respiratory and circulatory system conditions, such as cystic fibrosis and respiratory distress, had a higher asthma risk.
The researchers don't know how all of these factors influence asthma for better or worse.
Although they had no way to confirm that all asthma cases were correctly diagnosed, they note that many of their findings are in line with results from other asthma studies.